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781.
Underwater bubble plumes emerge from subsea releases of gas. They can be studied by mathematical models. Here an Eulerian-Lagrangian CFD model is presented. It accounts for relevant physics including buoyancy, turbulence, gas expansion and gas dissolution. The model is compared against three sets of experiments. There is consistency between model and experiments. Special focus is given to the effect of gas dissolution. It is demonstrated how the choice of mass transfer coefficient strongly affects the amount of gas dissolution. Since it is not apparent which mass transfer correlation is applicable, it is argued that more experimental data is needed. 相似文献
782.
The increasing availability of high resolution imagery has triggered the need for automated image analysis techniques, with reduced human intervention and reproducible analysis procedures. The knowledge gained in the past might be of use to achieving this goal, if systematically organized into libraries which would guide the image analysis procedure. In this study we aimed at evaluating the variability of digital classifications carried out by three experts who were all assigned the same interpretation task. Besides the three classifications performed by independent operators, we developed an additional rule-based classification that relied on the image classifications best practices found in the literature, and used it as a surrogate for libraries of object characteristics. The results showed statistically significant differences among all operators who classified the same reference imagery. The classifications carried out by the experts achieved satisfactory results when transferred to another area for extracting the same classes of interest, without modification of the developed rules. 相似文献
783.
Image segmentation remains a challenging problem for object-based image analysis. In this paper, a hybrid region merging (HRM) method is proposed to segment high-resolution remote sensing images. HRM integrates the advantages of global-oriented and local-oriented region merging strategies into a unified framework. The globally most-similar pair of regions is used to determine the starting point of a growing region, which provides an elegant way to avoid the problem of starting point assignment and to enhance the optimization ability for local-oriented region merging. During the region growing procedure, the merging iterations are constrained within the local vicinity, so that the segmentation is accelerated and can reflect the local context, as compared with the global-oriented method. A set of high-resolution remote sensing images is used to test the effectiveness of the HRM method, and three region-based remote sensing image segmentation methods are adopted for comparison, including the hierarchical stepwise optimization (HSWO) method, the local-mutual best region merging (LMM) method, and the multiresolution segmentation (MRS) method embedded in eCognition Developer software. Both the supervised evaluation and visual assessment show that HRM performs better than HSWO and LMM by combining both their advantages. The segmentation results of HRM and MRS are visually comparable, but HRM can describe objects as single regions better than MRS, and the supervised and unsupervised evaluation results further prove the superiority of HRM. 相似文献
784.
Very high resolution monitoring of landslide kinematics is an important aspect for a physical understanding of the failure mechanisms and for quantifying the associated hazard. In the last decade, the potential of Terrestrial Laser Scanning (TLS) to monitor slow-moving landslides has been largely demonstrated but accurate processing methods are still needed to extract useful information available in point cloud time series. This work presents an approach to measure the 3D deformation and displacement patterns from repeated TLS surveys. The method is based on the simplification of a 3D matching problem in a 2D matching problem by using a 2D statistical normalized cross-correlation function. The computed displacement amplitudes are compared to displacements (1) calculated with the classical approach of Iterative Closest Point and (2) measured from repeated dGPS observations. The performance of the method is tested on a 3 years dataset acquired at the Super-Sauze landslide (South French Alps). The observed landslide displacements are heterogeneous in time and space. Within the landslide, sub-areas presenting different deformation patterns (extension, compression) are detected by a strain analysis. It is demonstrated that pore water pressure changes within the landslide is the main controlling factor of the kinematics. 相似文献
785.
Terence J. Hirst 《Marine Georesources & Geotechnology》2013,31(4):371-373
Ocean Floor Mining by John S. Pearson. Noyes Data Corporation, Park Ridge, New Jersey, 1975. 201 pp., $24.00. Offshore Drilling Technology by Frank R. Carmichael. Noyes Data Corporation, Park Ridge, New Jersey, 1975. 392 pp., $36.00. 相似文献
786.
V. Ansan D. Loizeau S. Le Mouélic F. Poulet A. Lucas A. Gendrin Y. Langevin S. Murchie G. Neukum 《Icarus》2011,211(1):273-304
The 174 km diameter Terby impact crater (28.0°S-74.1°E) located on the northern rim of the Hellas basin displays anomalous inner morphology, including a flat floor and light-toned layered deposits. An analysis of these deposits was performed using multiple datasets from Mars Global Surveyor, Mars Odyssey, Mars Express and Mars Reconnaissance Orbiter missions, with visible images for interpretation, near-infrared data for mineralogical mapping, and topography for geometry. The geometry of layered deposits was consistent with that of sediments that settled mainly in a sub-aqueous environment, during the Noachian period as determined by crater counts. To the north, the thickest sediments displayed sequences for fan deltas, as identified by 100 m to 1 km long clinoforms, as defined by horizontal beds passing to foreset beds dipping by 6-10° toward the center of the Terby crater. The identification of distinct sub-aqueous fan sequences, separated by unconformities and local wedges, showed the accumulation of sediments from prograding/onlapping depositional sequences, due to lake level and sediment supply variations. The mineralogy of several layers with hydrated minerals, including Fe/Mg phyllosilicates, supports this type of sedimentary environment. The volume of fan sediments was estimated as >5000 km3 (a large amount considering classical martian fan deltas such as Eberswalde (6 km3)) and requires sustained liquid water activity. Such a large sedimentary deposition in Terby crater is characteristic of the Noachian/Phyllosian period during which the environment favored the formation of phyllosilicates. The latter were detected by spectral data in the layered deposits of Terby crater in three distinct layer sequences. During the Hesperian period, the sediments experienced strong erosion, possibly enhanced by more acidic conditions, forming the current morphology with three mesas and closed depressions. Small fluvial valleys and alluvial fans formed subsequently, attesting to late fluvial processes dated as late Early to early Late Hesperian. After this late fluvial episode, the Terby impact crater was submitted to aeolian processes and permanent cold conditions with viscous flow features. Therefore, the Terby crater displays, in a single location, geologic features that characterize the three main periods of time on Mars, with the presence of one of the thickest sub-aqueous fan deposits reported on Mars. The filling of Terby impact crater is thus one potential “reference geologic cross-section” for Mars stratigraphy. 相似文献
787.
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790.
影像匹配中金字塔数据结构比较与快速算法 总被引：10，自引：0，他引：10
分析了多种金字塔数据结构的生成方法 ,比较了不同方法在影像匹配中的优劣 ,并提出了一种影像金字塔生成的快速算法。 相似文献